Method and system for message transmission and reception

ABSTRACT

Wireless devices may contain multiple radio transceivers, each conforming to different communication protocols. A first transceiver conforming to a first communication protocol in a first wireless device may be able to receive, detect, and/or decode messages transmitted by a second transceiver in a second wireless device conforming to a second communication protocol. The first transceiver may communicate received, detected, and/or decoded information to a different transceiver in the same first wireless device, thus enabling the collocated transceivers to work in concert efficiently. A wideband transceiver using a set of multiple sub-channels in parallel may receive, detect, and/or decode messages transmitted by a narrowband transceiver using a set of multiple channels serially, thereby reducing scan time and power consumption.

RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.12/245,592 entitled: “Method And System For Message Transmission AndReception” filed Oct. 3, 2008 which claims priority of U.S. ProvisionalPatent Application 61/049,282, entitled “WLAN Assisted Bluetooth InquiryAnd Paging” filed Apr. 30, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to wirelesscommunication systems, and more particularly to wireless personal areanetworking and wireless local area networking.

2. Description of the Related Art

Wireless communication systems transfer data from a transmitting stationto one or more receiving stations using modulated radio frequency (RF)signals. Bluetooth™ systems are wireless communication systems governed,in part, by the Bluetooth™ Special Interest Group (SIG) which publishesspecifications and compliance standards. Current Bluetooth™ devices thatfollow the Bluetooth™ standards, up to version 2.1, use an inquiry scanprocedure to discover new devices and a page scan procedure to connectto connectable devices. The inquiry scan and page scan procedures maytake many seconds to complete because a Bluetooth™ transceiver listensfor the inquiry and page messages across a series of relatively narrowradio frequency channels, while a Bluetooth™ transceiver transmits on apotentially different series of narrow radio frequency channels.Wireless local area networking (WLAN) devices are generally governed bythe specifications and rules specified by the IEEE 802.11 working group.The IEEE 802.11b, 802.11g and 802.11n wireless local area networkingstandards provide exemplary wider bandwidth transmission methods thatmay use the same radio frequency band as Bluetooth™ standards. Portableelectronic devices such as laptop computers, personal digital assistantsand cellular telephones may incorporate hardware to support multiplewireless standards in the same device.

Both the Bluetooth™ and IEEE 802.11b/g/n wireless standards may use theunlicensed industrial scientific medical (ISM) frequency band from about2.4 GHz to 2.5 GHz including guard bands at the upper and lowerboundaries. Bluetooth™ physical layer radio channels may frequency hopamong a set of 79 different 1 MHz wide radio frequency channels, whilean IEEE 802.11 physical layer radio channel may occupy a 20 MHz or 40MHz contiguous frequency band. As Bluetooth™ devices may be designed forlow power consumption, reducing the time required to complete an inquiryor page procedure may reduce power consumed also.

Thus, there exists a need for a wireless radio reception method thatuses a wider bandwidth transceiver in combination with a wide or narrowbandwidth transceiver to shorten the discovery and connect proceduresthereby conserving energy within a wireless communication system.

SUMMARY OF THE INVENTION

Wireless devices may contain multiple radio transceivers, eachconforming to different communication protocols. A first transceiverconforming to a first communication protocol in a first wireless devicemay be able to receive, detect, and/or decode messages transmitted by asecond transceiver in a second wireless device conforming to a secondcommunication protocol. The first transceiver may communicate received,detected, and/or decoded information to a different transceiver in thesame first wireless device, thus enabling the collocated transceivers towork in concert efficiently. A wideband transceiver using a set ofmultiple sub-channels in parallel may receive, detect, and/or decodemessages transmitted by a narrowband transceiver using a set of multiplechannels serially, thereby reducing scan time and power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art dual radio communication device operatingon two wireless networks.

FIG. 2 illustrates a dual wireless radio device receiving signals from aBluetooth™ device through an IEEE 802.11 RF interface.

FIG. 3 illustrates a set of time slots for inquiry messaging in aBluetooth™ piconet.

FIG. 4 illustrates a flowchart for receiving a Bluetooth™ inquirymessage through an IEEE 802.11 RF interface and responding through aBluetooth™ RF interface.

FIG. 5 illustrates signal processing blocks in a dual wireless radiodevice receiving signals for a Bluetooth™ device through an IEEE 802.11RF interface and a Bluetooth™ interface.

FIG. 6 illustrates signal processing blocks in a dual wireless radiodevice receiving signal through an IEEE 802.11 RF interface andprocessing multiple Bluetooth™ correlations in the time domain.

FIG. 7 illustrates signal processing blocks in a dual wireless radiodevice receiving signals through an IEEE 802.11 RF interface andprocessing multiple correlations in the frequency domain.

FIG. 8 illustrates signal processing blocks in a dual wireless radiodevice transmitting Bluetooth™ signals on multiple sub-carriers througha modified IEEE 802.11 RF interface.

DETAILED DESCRIPTION

Electronic devices may include both a Bluetooth™ transceiver and an IEEE802.11 transceiver. A wider bandwidth transceiver, such as an IEEE802.11 transceiver, may listen for Bluetooth™ transmissions across arange of frequencies simultaneously and may shorten inquiry and pagescan procedures that establish and maintain connections in a Bluetooth™network. An IEEE 802.11 radio transceiver may listen to many Bluetooth™1 MHz wide radio frequency channels simultaneously, thus increasing theprobability of detecting an inquiry or page message successfully in ashorter time than a Bluetooth™ radio transceiver that listens to only asingle 1 MHz wide radio frequency channel at a time.

A Bluetooth™ piconet may consist of a master device and multiple slavedevices. Although master and slave roles may not be defined prior to theestablishment of a connection in the Bluetooth™ piconet, an inquiringdevice may be referred to as the master device, while an inquiryscanning device may be referred to as the slave device. The Bluetooth™master device may periodically transmit inquiry messages containing ageneral or dedicated inquiry access code by modulating a series of 32carrier frequencies distributed over a set of 79 possible carrierfrequencies spaced 1 MHz apart in the ISM band. For inquiry scan, theset of 32 frequencies and their frequency hopping sequence may beselected based on a calculation using a general inquiry access code(GIAC). Each inquiry message may consist of 68 bits transmitted at arate of 1 Mbit per second within a single 1 MHz frequency channel andmay occupy 68 micro-seconds of a 312.5 micro-second transmit interval,i.e. half of a 625 micro-second time slot. The inquiry message may berepeated within a second, different 1 MHz frequency channel in asucceeding 312.5 micro-second transmit interval. An inquiry frequencyhopping sequence may determine the succession of frequencies on whichthe master device may transmit the inquiry messages. Bluetooth™ systemsmay use a time division duplex transmission method alternating betweentransmit time slots used for master to slave communication and receivetime slots used for slave to master communication. The inquiry messagemay be sent repeatedly on a sequential train of 16 different frequenciesduring a series of transmit timeslots, cycling through the set of 16frequencies 256 times for a total duration of 1.28 seconds. TheBluetooth™ master device may then send the inquiry message on adifferent train of 16 frequencies chosen from the set of 32 possiblefrequencies during each subsequent 1.28 second interval.

A Bluetooth™ slave device may listen (scan) for an inquiry messagetransmitted within a single 1 MHz frequency channel during an inquiryscan window of 11.25 msec out of an inquiry scan interval of 1.28seconds. During the 18 consecutive 625 micro-second time slots spanningthe inquiry scan window of 11.25 msec, the Bluetooth™ master maytransmit within up to 16 different frequencies channels; however, theBluetooth™ slave may listen on one of the 16 frequencies not transmittedout of the 32 possible frequencies. During each succeeding inquiry scanwindow, the Bluetooth™ slave may listen on a different 1 MHz frequencychannel following an inquiry scan frequency hopping sequence.Eventually, the Bluetooth™ slave may listen to one of the frequencychannels when the Bluetooth™ master may transmit an inquiry message onthe same frequency channel; however, multiple successive inquiry scanintervals may occur thereby extending the time for the scan procedure tocomplete. A benefit of the invention is to reduce the time for the scanprocedure by using a transceiver that listens to multiple 1 MHzfrequency channels simultaneously increasing the likelihood of observingthe Bluetooth™ master device's transmitted inquiry message.

FIG. 1 illustrates a wireless communication system including threewireless devices, a first device including two wireless transceiversusing two communication protocols, a second wireless device including awireless transceiver using one of the two communication protocols and athird wireless device including a wireless transceiver using the otherof the two communication protocols. More specifically, FIG. 1 providesan exemplary architecture for a dual radio communication device 100including a Bluetooth™ transceiver (blocks 101, 103, 105) and an IEEE802.11 transceiver (blocks 102, 104, 106). The blocks 101-106 mayrepresent the functions associated with the layers in the standard OSIseven layer communications protocol stack. Communication between blocksvertically, i.e. between a given layer and the next higher or lowerlayer, while not indicated explicitly in FIG. 1, may exist for thecommunication protocol stack to function. The dual radio device 100 mayinclude an IEEE 802.11 WLAN radio frequency (RF) block 106 and aBluetooth™ RF block 105 that transmit and receive separate signals 107,108 from an IEEE 802.11 device 120 and a Bluetooth™ device 110respectively. The dual radio device 100 may communicate on two parallelcommunication networks, a Bluetooth™ personal area network (PAN) 130 andan IEEE 802.11 wireless local area network (WLAN) 140. Limitedcommunication between the Bluetooth™ and IEEE 802.11 transceivers withinthe dual radio communication device 100 may seek to minimizeinterference between transmissions on the Bluetooth™ PAN 130 andtransmissions on the IEEE 802.11 WLAN 140. For example, the Bluetooth™higher layer 101 and the IEEE 802.11 higher layer 102 in the dual radiocommunication device 100 may communicate with each other to coordinatetransmissions on the Bluetooth™ PAN 130 and the IEEE 802.11 WLAN 140 tominimize overlapping frequencies or to share by time division a set ofoverlapping frequencies. Alternatively, without communication betweenthem, the Bluetooth™ and 802.11 transceivers may each examine one ormore frequency bands prior to transmitting to avoid frequencies used bythe other system's transceiver. For any of these techniques, onetransceiver may treat the transmissions of the other transceiver as“noise” to ignore rather than as an information carrying “signal” todecode. The present invention recognizes that an IEEE 802.11 transceivermay be able to detect and decode a Bluetooth™ inquiry or page messagequicker than a Bluetooth™ transceiver, and a dual radio device maybenefit as a result.

FIG. 2 illustrates a wireless communication system in which a dual radiocommunication device 200 may communicate with the Bluetooth™ device 110through a Bluetooth™ RF block 205 and through an IEEE 802.11 RF block206. Information received from or transmitted to the Bluetooth™ device110 by the IEEE 802.11 RF block 206 may be communicated within the dualradio device 200 between the higher layer blocks 201 and 202 and/orbetween the middle layer blocks 203 and 204. Examples of informationcommunicated between the transceivers are detailed later. Note that thefunctional blocks of the dual radio communication device 200 may berealized using a number of different architectures. Some processingblocks in both the Bluetooth™ transceiver and the IEEE 802.11transceiver may be realized in common processing units or alternativelyin separately dedicated processing units. Some embodiments of the dualradio communication device 200 may use a common antenna and/or a commonanalog front end to realize the Bluetooth™ RF 205 and IEEE 802.11 RF 206blocks for example. The Bluetooth™ higher layers block 201 and the IEEE802.11 higher layers block 202 may also be realized in a commonprocessing core. Any variant architecture that includes both aBluetooth™ transceiver and an IEEE 802.11 transceiver may benefit fromthe invention disclosed herein.

As illustrated in FIG. 2, the dual radio communication device 200 mayinclude an IEEE 802.11 wireless local area networking (WLAN) basebandprocessing block 204 containing one or more fast Fourier transform (FFT)processing blocks that may listen to one or more 20 MHz wide contiguousbands of radio frequencies in the ISM band. (Depending on the samplingrate into and processing rate of the FFT block, a sub-band of or theentire ISM band may be monitored.) The Bluetooth™ device 110 maytransmit, at least in part, within a portion of the band of radiofrequencies on which the IEEE 802.11 transceiver may listen. Duringcommunication on an IEEE 802.11 WLAN, e.g. from the IEEE 802.11 device120 through the IEEE 802.11 RF block 206 via the path 209, the IEEE802.11 WLAN baseband processing block 204 may compute a set of receivesymbols transmitted using an orthogonal frequency division multiplexing(OFDM) method. In the absence of an IEEE 802.11 transmission via thepath 209, the IEEE 802.11 WLAN baseband processing block 204 may computethe presence of other signals within the same set of frequenciesnormally occupied by a set of OFDM symbols, e.g. transmissions from theBluetooth™ device 110 through the IEEE 802.11 RF transceiver 206 via thepath 207.

Two different reception embodiments may be considered for a dual radiocommunication device 200 that includes both an IEEE 802.11 transceiverand a Bluetooth™ transceiver. In a first reception embodiment, the IEEE802.11 baseband processing block 204 may detect the presence of aBluetooth™ inquiry message transmitted by the Bluetooth™ device 110through path 207 and may alert the Bluetooth™ transceiver on whichfrequencies to decode the Bluetooth™ inquiry message. The IEEE 802.11baseband processing block 204 may alert the Bluetooth™ transceiver bycommunicating directly with the Bluetooth™ baseband/link layer block 203or may communicate through the IEEE 802.11 higher layers block 202 andthe Bluetooth™ higher layers block 201. In a second receptionembodiment, the IEEE 802.11 baseband processing block 204 may bothdetect and decode a Bluetooth™ inquiry message and then may communicateto the Bluetooth™ transceiver the received inquiry message. In eitherembodiment, the Bluetooth™ transceiver within the dual radiocommunication device 200 may respond to the inquiry message bytransmitting to the Bluetooth™ device 110 through path 208. Details ofthe embodiments are described below.

In the first reception embodiment, the output of an FFT processing blockin the IEEE 802.11 baseband/MAC layer block 204 may consist of a set ofcomplex values, each complex value associated with a different radiofrequency sub-channel spread across a bandwidth of 20 MHz in the ISMband. The number of different frequency sub-channels may depend on thesize of the FFT; e.g. an IEEE 802.11 baseband processor may calculate aset of complex values for 64 frequency sub-channels spaced 312.5 kHzapart based on a set of time samples received during a 4 micro-secondinterval. As a Bluetooth™ inquiry or page message extends for 68micro-seconds on a single carrier frequency, the IEEE 802.11baseband/MAC layer block 204 may have sufficient time to detect thepresence of the Bluetooth™ inquiry or page message by processing one ormore sets of time samples received during one or more 4 micro-secondintervals.

Note that Bluetooth™ carrier frequencies may be spaced 1 MHz apart, so aBluetooth™ transceiver's single frequency energy in one 1 MHz frequencychannel may appear in more than one of the IEEE 802.11 baseband/MAClayer block's frequency sub-channels spaced 312.5 kHz apart output bythe FFT processing block. In some embodiments, the processing rate andsize of an FFT processing block may be flexible, enabling values to beset to match those of Bluetooth transceivers. For example, using a 128point FFT with an input sample rate of 128 MHz may result in a set of128 complex values every 1 μsec, i.e. at 1 MHz, matching the symbol rateof a Bluetooth™ transceiver. In this case, a Bluetooth™ transceiver'ssingle frequency energy in one 1 MHz frequency channel may appearprimarily in one of the frequency sub-channels spaced 1 MHz apart outputby an FFT processing block.

Additionally, Bluetooth™ transceivers may use Gaussian Frequency ShiftKeying (GFSK) modulation in which the Bluetooth™ carrier frequency maybe shifted by at least +115 kHz from a nominal frequency for a binaryone and by at least −115 kHz from the nominal frequency for a binaryzero at a rate of 1 MHz, i.e. every one micro-second a new bit may betransmitted. Using an energy threshold detector that estimates thepresence or absence of a signal on the set of frequencies output fromthe FFT processing block, an 802.11 baseband/MAC layer block 204 maydetermine on which frequency the Bluetooth™ device 110 may betransmitting an inquiry message, distinguishing the Bluetooth™ signalfrom background noise. With additional processing as described below, anoutput from an FFT processing block may also be used to estimate the bitpattern of an inquiry message sent by the Bluetooth™ device 110.

As illustrated in FIG. 3, a Bluetooth™ system may divide transmissionsinto a series of transmit (TX) master-to-slave time slots and receive(RX) slave-to-master time slots each time slot extending 625micro-seconds. Note that the timeslots in FIG. 3 are labeled TX or RXfrom the point of view of the master (inquiring) device. During a firsttime slot 301, an inquiring (master) device may send an inquiry messageconsisting of a 68 bit inquiry access code at a rate of 1 Mbit/sec for afirst 68 micro-second interval 310 on a first frequency f₁ during afirst portion of the first time slot 301 and then may repeat the inquirymessage for a second 68 micro-second interval 311 on a second frequencyf₂ during a second portion of the first time slot 301. During a secondtime slot 302 immediately following the first time slot 301, an inquiryscanning (slave) device may respond to the inquiry message by sending aninquiry response message during a 68 micro-second interval 312 on afirst response frequency f′₁ or during a second interval 313 on a secondresponse frequency f′₂. If the inquiring (master) device does notreceive an inquiry response message during the second time slot 302,then the inquiring (master) device may repeat the same inquiry messageduring a third time slot 303 modulating a third frequency f₃ and afourth frequency f₄. If the inquiry scanning (slave) device respondsduring a fourth time slot 304, then the inquiry scanning (slave) devicemay send an inquiry response message modulating a third responsefrequency f′₃ or a fourth response frequency f′₄. Likewise, during timeslot 305, an inquiring (master) device may send an inquiry messageconsisting of a 68 bit inquiry access code at a rate of 1 Mbit/sec for afirst 68 micro-second interval 314 on a first frequency f₁ during afirst portion of the first time slot 314 and then may repeat the inquirymessage for a second 68 micro-second interval 315 on a second frequencyf₂ during a second portion of time slot 305. During time slot 306immediately following time slot 305, an inquiry scanning (slave) devicemay respond to the inquiry message by sending an inquiry responsemessage during a 68 micro-second interval 316 on a first responsefrequency f′₁ or during a second interval 317 on a second responsefrequency f′₂.

The inquiry and inquiry response frequency hopping sequences used by theinquiring (master) device and the inquiry scanning (slave) devicerespectively may be in part determined by a general inquiry access code(GIAC) transmitted in the inquiry message. As such, the inquiry scanning(slave) device may need to decode the inquiry message before respondingto the inquiring (master) device, as the inquiry scanning (slave) devicemay not know a priori the inquiry response frequency hopping sequence.Knowing which frequency on which the inquiring (master) devicetransmitted an inquiry message alone may be insufficient to determinethe inquiry response frequency hopping sequence. The inquiring (master)device may also transmit a dedicated inquiry access code (DIAC), ratherthan a GIAC, to which only certain slave devices may respond. Theinquiry scanning (slave) device may detect which frequency on which theinquiring (master) device transmitted an inquiry message, but theinquiry scanning (slave) device may not know whether to respond withoutdecoding the inquiry message.

To conserve power consumption, e.g. in a battery operated version of thedual radio device 200, a Bluetooth™ transceiver may be in “sleep mode”awaiting the presence of an inquiry message. In order to “waken” theBluetooth™ transceiver to capture and decode the inquiry message, theIEEE 802.11 baseband processor 204 may detect the inquiry message duringthe first few micro-seconds of receiving the inquiry message, e.g. basedon energy received from the first few bits of the 68 bit long inquirymessage in a number of receive frequencies output by the FFT processingblock. The IEEE 802.11 transceiver may alert the Bluetooth™ transceiveron which frequency to begin receiving the inquiry message bycommunicating between the middle layer blocks 204 and 203 or between thehigher layer blocks 202 and 201. As the Bluetooth™ transceiver may“sleep” during a number of micro-seconds of the inquiry message, theIEEE 802.11 baseband processor 104 may provide a set of time domainsamples that include at least a period from the beginning of the inquirymessage to a point when the Bluetooth™ transceiver begins receiving andsampling the inquiry message through its Bluetooth™ RF block 205.Preferably the set of time domain samples may be formatted to minimizecalculations required by the Bluetooth™ transceiver to decode theinquiry message. Thus a first portion of a Bluetooth™ inquiry messagemay be received from the Bluetooth™ device 110 through the IEEE 802.11RF block 206 via path 207 and a second portion of the same Bluetooth™inquiry message may be received through the Bluetooth™ RF block 205 viapath 208.

In the second reception embodiment of the invention, the IEEE 802.11baseband processing block 204 may calculate an FFT sufficiently quicklythat each one micro-second long bit of a 68 micro-second inquiry messagemay be detected and decoded as a “one” or a “zero” individually. The FFTprocessing block in the IEEE 802.11 baseband processing block 204 mayoutput a set of complex values every one micro-second rather than everyfour micro-seconds. With such a quick FFT, the IEEE 802.11 basebandprocessing block 204 may determine both a carrier frequency used by theBluetooth™ device 110 for transmitting the inquiry message and theinquiry access code, i.e. the actual 68 bit transmitted sequence. TheIEEE 802.11 baseband processing block 204 may then transmit the receivedinquiry message and the determined carrier frequency to the Bluetooth™transceiver. The Bluetooth™ transceiver may respond to the inquirymessage in a subsequent receive scan time slot on an appropriate carrierfrequency based on the information provided by the IEEE 802.11 basebandprocessing block 204. For example a Bluetooth™ inquiry scanning devicemay respond on carrier frequency f′₁ in time slot 302 after receiving adecoded inquiry access code from the IEEE 802.11 baseband processingblock 204 during time slot 301. Alternatively a Bluetooth™ inquiryscanning device may confirm a decoded inquiry access code provided bythe IEEE 802.11 baseband processing block 204 during a first portion oftime slot 301 by listening to receive the same inquiry access code onfrequency f₂ during a second portion of time slot 301 before respondingto the inquiry message in time slot 302 on either frequency f′₁ orfrequency f′₂.

FIG. 4 illustrates a flowchart of several exemplary method steps of theinvention indicating the operations and interactions of thecomputational blocks of the devices in FIG. 2 following a portion of theinquiry messaging sequence of FIG. 3. Starting at the top of theflowchart in step 401, the Bluetooth™ device 110 may transmit an inquirymessage 310 on carrier frequency f₁ in time slot 301. The IEEE 802.11 RFinterface 206 in the dual radio Bluetooth™/IEEE 802.11 device 200 mayreceive at least a portion of the inquiry message 310 (step 402). TheIEEE 802.11 Baseband/MAC layer 204 may detect the inquiry message 310and may identify the carrier frequency f₁ on which the message wastransmitted. Following step 403 in FIG. 4, the method may proceed alongone of three different branches as outlined by the dashed boxes 420(left column), 430 (center column) and 440 (right column). Each branchof the method may advantageously allow portions of the dual radiocommunication device 200 configured to process WLAN signals to assist inthe processing of Bluetooth™ signals.

In the left column 420 starting in step 404, the IEEE 802.11Baseband/MAC layer 204 may identify the carrier frequency f₁ to theBluetooth™ Baseband/Link layer 203, either directly or through thehigher layers 202 and 201. The Bluetooth™ RF block 205 may awaken andmay listen for a subsequent inquiry message on carrier frequency f₁,receiving an inquiry message 314 in time slot 305 (step 405). Note thatthe Bluetooth™ RF block 205 after waking up may have missed a firstportion of the inquiry message 310 in time slot 301, thus the Bluetooth™RF block 205 may wait for the next inquiry message 314 transmitted onthe carrier frequency f₁ which may occur in time slot 305. TheBluetooth™ Baseband/Link Layer 203 may decode the received inquirymessage 314 (step 406) and may respond by transmitting an inquiryresponse message 316 by modulating carrier frequency f′₁ in time slot306 (step 407).

FIG. 5 illustrates an exemplary embodiment of select processing blocksin a dual radio device that may implement the method illustrated in theleft column 420 of FIG. 4. Inside the IEEE 802.11 RF block 206, an IEEE802.11 analog front end 501 may receive from an antenna Bluetooth™signals that may be sampled by an A/D converter 502 before beingtransformed by an FFT block 503 in the IEEE 802.11 baseband/MAC layerblock 204. The output of the FFT block 503 may provide a set of complexvalues for a set of frequencies to an energy detection block 504, whichmay determine if a Bluetooth™ inquiry message has been received on aparticular frequency. The frequency detected may then be communicated toa Bluetooth™ analog front end 505 within the Bluetooth™ RF block 205indicating on which frequency channel the Bluetooth™ transceiver mayreceive a message. A received digital signal output from an Analog toDigital converter 506 in the Bluetooth™ RF block 205 may be processed bya finite impulse response (FIR) filter 508 and then by a correlationblock 509 in the Bluetooth™ baseband/MAC layer block 203 to detect aBluetooth™ inquiry message. Note that while FIG. 5 illustrates an IEEE802.11 analog front end 501 that may use 20 or 40 MHz of bandwidth, thesame device may use a modified analog front end with wider analogfilters and higher A/D sampling to cover a wider bandwidth, for example128 MHz that may span the entire ISM band. The energy detection block504 may also determine if one or more Bluetooth™ inquiry message havebeen received on one or more frequencies rather than just the onefrequency described in FIG. 4 and shown in FIG. 5. Multiple frequenciesmay be communicated by the energy detection block 504 to the Bluetooth™baseband/link layer block 203 so that the Bluetooth™ transceiver maylook for inquiry messages on one or more frequencies.

A second method may follow the center column 430 of FIG. 4. Starting instep 408, the IEEE 802.11 Baseband/MAC layer 204 may store a set of timedomain samples received by the IEEE 802.11 RF block 206 that may includea first part of the received inquiry message 310. The IEEE 802.11Baseband/MAC layer 204 may identify the detected carrier frequency f₁and may communicate the saved time domain samples to the Bluetooth™Baseband/Link Layer block 203 (step 409). The Bluetooth™ RF block 205may awaken and receive a second part of the inquiry message 310 oncarrier frequency f₁ in time slot 301 (step 410). The Bluetooth™Baseband/Link Layer block 203 may decode the inquiry message 310 bycombining the first part of the received inquiry message 310 based onthe saved time domain samples received through the IEEE 802.11 RF block206 and the second part of the received inquiry message 310 receivedthrough the Bluetooth™ RF block 205 (step 411). The Bluetooth™Baseband/Link Layer 203 may respond to the inquiry message 310 bytransmitting an inquiry response message 312 on carrier frequency f′₁ intime slot 302 (step 412).

FIG. 6 illustrates an exemplary embodiment of select processing blocksin a dual radio device that may implement the method illustrated in thecenter column 430 of FIG. 4. As in FIG. 5, the IEEE 802.11 analog frontend 501 in the IEEE 802.11 RF block 206 may receive a Bluetooth™ signalfrom an antenna, and a digitally sampled version of the Bluetooth™signal may be input to the FFT block 503 in the IEEE 802.11 Baseband/MAClayer block 204. As the FFT block 503 may transform a set of samples inparallel, a buffer 601 may store a set of inputs before the FFTprocessing, and a subset of these stored inputs may also be transmittedto the Bluetooth™ baseband/link layer block 203 and combined with adigital frequency signal therein. A frequency generator block 507 in theBluetooth™ baseband/link layer block 203 may generate the digitalfrequency signal based on information communicated from the energydetection block 504 in the IEEE 802.11 baseband/MAC layer block 204.Note that multiple frequencies may be detected by the energy detectionblock 504, and multiple Bluetooth™ frequencies may be filtered andcorrelated in parallel in the Bluetooth™ baseband/link layer block 203using a bank of FIR filters 508 and correlation blocks 509. In thismanner, the Bluetooth™ transceiver in a dual radio device 200 may detectinquiry messages simultaneously from multiple Bluetooth™ devices thateach may transmit on different frequency channels. This parallelprocessing may speed the completion of an inquiry procedure between aBluetooth™ master (inquiring) device and multiple Bluetooth™ slave(inquiry scanning) devices.

A third method may follow the right column 440 of FIG. 4. Starting instep 413, the IEEE 802.11 Baseband/MAC layer 204 may decode the receivedinquiry message 310. The IEEE 802.11 Baseband/MAC layer 204 may identifythe detected carrier frequency f₁ and may communicate the receiveddecoded inquiry message 310 to the Bluetooth™ Baseband/Link Layer block203. The Bluetooth™ Baseband/Link Layer 203 may respond to the inquirymessage 310 by transmitting an inquiry response message 312 bymodulating the carrier frequency f′₁ in time slot 302 (step 415).

FIG. 7 illustrates an exemplary embodiment of select processing blocksin a dual radio device that may implement the method illustrated in theright column 440 of FIG. 4. In this embodiment, Bluetooth™ messages maybe detected and decoded on one or more frequency sub-channels usingblocks in the IEEE 802.11 Baseband/MAC layer 204. Each Bluetooth™ symbolmay occupy a time span of one psec, and a 128 point FFT transforming aset of samples from a 128 MHz sampling Analog to Digital converter mayresult in one complex value per frequency sub-channel spaced 1 MHz apartacross a 128 MHz bandwidth. Other A-to-D sampling rates and FFT sizesmay also be used that result in frequency sub-channels spaced 1 MHzapart, for example a 64 point FFT transforming a set of samples from a64 MHz sampling A-to-D converter. While these frequency domain samplesmay provide enough information for energy detection, as described forFIGS. 5 and 6, additionally calculating the actual positive or negativefrequency shift of the Bluetooth™ frequency carrier to determine the bitvalue may require additional processing. An FFT frame of 128 samplesinput to a 128 point FFT may not align with a transmitted Bluetooth™symbol boundary, and thus an FFT block 701 may transform together partof one transmitted Bluetooth™ symbol and part of a subsequentlytransmitted Bluetooth™ symbol.

In an embodiment of the invention, the FFT block 701 may operate atleast at twice the processing rate compared with the sample rate of theAnalog to Digital converter 502, computing at least two FFT transformsfor each Bluetooth™ symbol (bit) period of one psec. One FFT transformmay be shifted by one half of a Bluetooth™ symbol period with respect tothe other FFT transform. For example the FFT block 701 may transform aset of samples {x[0], x[1], . . . , x[127]} followed by a set of samples{x[64], x[65], . . . , x[191]} followed by a set of samples {x[128],x[129], . . . , x[255]}, etc. thereby using each sample from the Analogto Digital converter 502 twice. One of the transforms may contain atleast ¾ of one Bluetooth™ symbol together with at most ¼ of a secondBluetooth™ symbol, which may provide sufficient information to decodewhich bit was transmitted. The GFSK modulation method used by theBluetooth™ standard may encode a “one” as a positive shift in frequencyand a “zero” as a negative shift in frequency. As the FFT block 701 mayintegrate the frequency change over time in its FFT transform, a “one”bit value may still result in a positive phase shift on the associatedfrequency sub-channel output from the FFT block 701, while a “zero” maystill result in a negative phase shift, even if the next Bluetooth™symbol, of which part may be transformed together with the currentBluetooth™ symbol, may encode a different bit value. Operating the FFTblock 701 at twice the Analog to Digital converter 502 sampling rateprovides sufficient information to decode the GFSK modulated Bluetooth™symbols; higher rates such as three or four times the sampling rate ormore may also be used.

A set of samples output from the FFT block 701 may be processed by anenergy detection and frequency calculation block 702. Of the 128frequency sub-channels spaced 1 MHz apart, up to 79 frequencysub-channels may contain information from a Bluetooth™ message ingeneral, but up to only 32 frequency sub-channels may containinformation for Bluetooth™ inquiry (or page) messages. The energydetection and frequency calculation block 702 may process only a subsetof all of the FFT block 701 outputs to minimize computations. For eachfrequency sub-channel on which energy may be detected, the quantitysign(x[n]·conj(x[n−2]) may be computed by the energy detection andfrequency calculation block 701 to determine the frequency and therebythe bit received on that frequency sub-channel. The calculation may beperformed twice, once for each FFT “phase”, and the best result may beused. A set of resulting demodulated bits may be transferred through afrequency selection block 703 that may route the results to a bank ofcorrelation blocks 509. Each correlation block 509 may determine whethera particular bit pattern may be received on a particular frequencysub-channel. The frequency sub-channel associated with each correlationblock 509 may be changed based on which frequency sub-channels aredetected in the energy detection and frequency calculation block 702. ABluetooth™ message detected by a correlation block 509 may betransmitted, along with the associated frequency sub-channel, to theBluetooth™ baseband/link layer 203 as indicated in step 414 of FIG. 4.

Each of the three methods illustrated in FIG. 4 may offer varyingoptions to balance processing capabilities in the Bluetooth™ and IEEE802.11 blocks of the dual radio Bluetooth™/IEEE 802.11 device 200. Theleft column 420 method may require minimal computations by the IEEE802.11 Baseband/MAC layer block 204 but may take longer for theBluetooth™ Baseband/Link layer block 203 to respond to the inquirymessage 310. This delay may be due to waiting to receive the secondinquiry message 314 before responding. The center column 430 method mayrequire some additional computations for the Bluetooth™ Baseband/Linklayer block 203 to combine time samples from the IEEE 802.11 RF block206 and the Bluetooth™ RF block 205 to receive the inquiry message 310;however, the Bluetooth™ Baseband/Link layer block 203 may respond morequickly than using the left column 420 method. The right column 440method may require more computations by the IEEE 802.11 Baseband/MAClayer block 204 to decode the inquiry message 310, but the Bluetooth™Baseband/Link Layer block 203 may respond quickly to the inquiry message310 with minimal computations. Other variant embodiments of theinvention may be possible in addition to those illustrated in FIG. 4.

As described above for inquiry messages, the invention may apply also todetecting and decoding page messages transmitted by a Bluetooth™ paging(master) device and responded to by a Bluetooth™ page scanning (slave)device. Page messages may consist of a 68 bit sequence transmitted usinga page frequency hopping sequence in the same time slotted format asindicated for inquiry messages in FIG. 3. An IEEE 802.11 basebandprocessing block 204 in a dual radio IEEE 802.11/Bluetooth™ device 200may listen for Bluetooth™ page messages, may detect carrier frequencieson which such page messages are transmitted and may decode such pagemessages as described above for inquiry messages. Bluetooth™ pagemessages may differ from Bluetooth™ inquiry messages by their specificbit sequence and by the frequency hopping sequence used.

As described above for receiving Bluetooth™ messages on multiplefrequency sub-channels, dual radio devices 200 that include both aBluetooth™ transceiver and an IEEE 802.11 transceiver may also transmiton multiple frequency sub-channels. A wider bandwidth transceiver, suchas an IEEE 802.11 transceiver, may transmit Bluetooth™ messages across arange of frequencies simultaneously and may shorten inquiry and pagescan procedures that establish and maintain connections in a Bluetooth™network. An IEEE 802.11 radio transceiver in the dual radio device 200may transmit the same Bluetooth™ message on multiple Bluetooth™ 1 MHzwide radio frequency channels simultaneously, thus increasing theprobability that the Bluetooth™ transceiver 110 that may listen on onlya single 1 MHz wide radio frequency channel at a time may detect aninquiry or page message successfully in a shorter time.

FIG. 8 illustrates an example of how a Bluetooth™ message may bereplicated across multiple frequency channels using the IFFT of amodified IEEE 802.11 transceiver. A Bluetooth™ message generator 801 mayoutput a bit value at a 1 MHz rate to a Gaussian Frequency Shift Key(GFSK) modulation block 802 that may produce a Bluetooth™ bit pulse each1 μsec. The power spectrum of that bit pulse may be illustrated by thegraph 805. A frequency vector generator 803 may input a vector of 128ones and zeroes to a 128 point inverse Fast Fourier Transform (IFFT)block 804 that may produce a transformed set of outputs every 1 μsec.The block 804 may output a set of sinusoids (sub-carriers) at differentfrequencies, where frequency sub-carriers with a “one” input may containa non-zero energy sinusoid, while frequency sub-carriers with a “zero”input may contain no energy. The power spectrum of the output of theIFFT 804 may be a series of impulses spaced 1 MHz apart as indicated ingraph 806. Combining the output of the IFFT 804 with the output of theGFSK modulation block 802 using a mixer 809 may result in a signal witha power spectrum that replicates the Bluetooth™ bit pulse on each of thedifferent frequency sub-carriers as shown in graph 807. The combinedsignal may then be processed through a wideband analog front end, suchas a modified 802.11 IEEE analog block 808, for transmission through anantenna to multiple Bluetooth™ devices (not shown) simultaneously.

Although illustrative embodiments of the invention have been describedin detail herein with reference to the accompanying figures, it is to beunderstood that the invention is not limited to those preciseembodiments. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed. As such, many modificationsand variations will be apparent. Accordingly, it is intended that thescope of the invention be defined by the following Claims and theirequivalents.

1. A wireless communication device including: a first wirelesstransceiver conforming only to a first communication protocol that usesa series of frequency channels, one frequency channel at a time, from aset of frequency channels, and a second wireless transceiver conformingonly to a second communication protocol that uses a plurality offrequency sub-channels in parallel from a set of frequency sub-channels,wherein the second wireless transceiver is configured to detect acommunication message, transmitted on a frequency channel in the set offrequency channels by a third wireless transceiver conforming to thefirst communication protocol in a second wireless device, in one or morefrequency sub-channels in the set of frequency sub-channels and toidentify the frequency channel to the first wireless transceiver,wherein, based on such identification, the first wireless transceiver isconfigured to then respond to the communication message to the thirdwireless transceiver on the frequency channel.
 2. The device of claim 1wherein the second wireless transceiver is further configured tocommunicate a first portion of the communication message to the firstwireless transceiver.
 3. The device of claim 2 wherein the firstwireless transceiver is configured to receive a second portion of thecommunication message on the frequency channel and to decode thecommunication message.
 4. The device of claim 1 wherein the secondwireless transceiver is further configured to decode the communicationmessage transmitted by the third wireless transceiver and to communicatethe communication message to the first wireless transceiver.
 5. Thedevice of claim 1 wherein the second wireless transceiver is configuredto detect the communication message transmitted by the third wirelesstransceiver by measuring a received energy in one or more of theplurality of frequency sub-channels in the set of frequencysub-channels.
 6. The device of claim 1 wherein the first communicationprotocol is a frequency hopping spread spectrum protocol and the secondcommunication protocol is an orthogonal frequency division multiplexingprotocol.
 7. The device of claim 1 wherein the first communicationprotocol is a Bluetooth™ protocol and the second communication protocolis an IEEE 802.11 wireless protocol.
 8. The device of claim 7 whereinthe communication message is an inquiry message.
 9. The device of claim7 wherein the communication message is a page message.
 10. The device ofclaim 4 wherein the first communication protocol is a Bluetooth™protocol and the second communication protocol is an IEEE 802.11wireless protocol.
 11. The device of claim 10 wherein the communicationmessage is an inquiry message.
 12. The device of claim 10 wherein thecommunication message is a page message.
 13. A wireless communicationmethod comprising: receiving a communication message by a first wirelesstransceiver in a dual radio device, wherein the first wirelesstransceiver conforms only to a first communication protocol that uses aplurality of frequency sub-channels in parallel from a set of frequencysub-channels, and wherein the communication message was transmittedusing a second communication protocol that uses a subset of frequencychannels, one frequency channel at a time, from a set of frequencychannels; detecting, by the first wireless transceiver, thecommunication message on one or more frequency sub-channels in theplurality of frequency sub-channels; identifying, by the first wirelesstransceiver to a second wireless transceiver in the dual radio device, afrequency channel on which the communication message was transmitted,wherein the second wireless transceiver conforms only to the secondcommunication protocol, responding, by the second wireless transceiverbased on the identifying, to the communication message on the frequencychannel.
 14. The method of claim 13 further including communicating, bythe first wireless transceiver to the second wireless transceiver, afirst portion of the communication message.
 15. The method of claim 14further including receiving, by the second wireless transceiver, asecond portion of the communication message on the frequency channel,and decoding, by the second wireless transceiver, the communicationmessage.
 16. The method of claim 15 further including wakening thesecond wireless transceiver from a reduced power state before receivingthe second portion of the communication message on the frequencychannel.
 17. The method of claim 13 further including decoding, by thefirst wireless transceiver, the communication message; communicating, bythe first wireless transceiver to the second wireless transceiver, thecommunication message.
 18. The method of claim 13 wherein detecting thecommunication message includes measuring a received energy in one ormore of the plurality of frequency sub-channels in the set of frequencysub-channels.
 19. The method of claim 13 wherein the secondcommunication protocol uses the subset of frequency channels serially.20. The method of claim 13 wherein the first communication protocol isan orthogonal frequency division multiplexing protocol and the secondcommunication protocol is a frequency hopping spread spectrum protocol.21. The method of claim 13 wherein the first communication protocol isan IEEE 802.11 wireless protocol and the second communication protocolis a Bluetooth™ protocol.
 22. The method of claim 21 wherein thecommunication message is an inquiry message.
 23. The method of claim 21wherein the communication message is a page message.
 24. The method ofclaim 17 wherein the first communication protocol is an IEEE 802.11wireless protocol and the second communication protocol is a Bluetooth™protocol.
 25. The method of claim 24 wherein the communication messageis an inquiry message.
 26. The method of claim 24 wherein thecommunication message is a page message.